The present invention pertains to electrodes used in plasma processing.
Plasma processing systems are used in the manufacture and processing of semiconductors, integrated circuits, displays and other devices and materials, to remove material from or to deposit material on a substrate such as a semiconductor substrate. In some instances, these plasma processing systems use electrodes for providing RF energy to a plasma useful for depositing or removing material on a substrate.
There are several different kinds of plasma processes used during wafer processing. These processes include, for example: plasma etching, plasma deposition, plasma assisted photoresist stripping and in-situ plasma chamber cleaning.
When it is desired to deposit materials onto a semiconductor wafer, a plasma reactor is sometimes used to deposit a variety of materials, for example, copper or silicon dioxide, using techniques such as plasma enhanced chemical vapor deposition (PE-CVD) or physical vapor deposition (PVD). In copper PVD applications, a copper target, exposed to ion bombardment, is utilized to provide a source of material for deposition on a surface of the semiconductor wafer to form the desired wafer topography. In oxide film formation using chemical vapor deposition (CVD), for example, silane (SiH4) and N2O are introduced into the process chamber wherein the product SiO2 is adsorbed onto the wafer surface and the additional products diatomic hydrogen (H2) and diatomic nitrogen (N2) are pumped away.
A problem that has plagued prior art plasma reactors is the control of the plasma to obtain uniform workpiece etching and/or deposition. In plasma reactors, the degree of etch or deposition uniformity is determined by the uniformity of the plasma properties. The latter is dictated by the design of the overall system, and in particular the design of the electrodes used to create the plasma in the interior of the reactor chamber.
The present invention provides an electrode assembly for use in a plasma processing system including a base electrode adapted to be coupled to a source of RF energy, a removable electrode removably coupled to the base electrode, and a material interposed between a surface of the base electrode and a surface of the removable electrode.
In one embodiment, the material interposed between a surface of the base electrode and a surface of the metal electrode can be a thin film layer deposited for example on the surface of the removable electrode such that the thin layer comes in contact with the base electrode. Alternatively, the material interposed between a surface of the base electrode and a surface of the metal electrode can be a thin film layer deposited on the surface of the base electrode such that the thin layer comes in contact with the removable electrode.
In one embodiment, the removable electrode is comprised of a semiconductor material. In another embodiment, the removable electrode is comprised of silicon. In one embodiment the thin layer is deposited in a pattern such as, but not limited to, a plurality of concentric rings and pie-shapes. The thin layer deposited in each of the concentric rings or pie-shapes can be of different materials such as a material with different dielectric constant, an electrically conductive material or materials having different radio frequency loss characteristics.